Assembly kit for creating paddle-style lead from one or several percutaneous leads and method of lead implantation

ABSTRACT

In one embodiment, an assembly for conducting pulses from an implantable pulse generator, comprises: at least one percutaneous lead comprising terminals and at least two groups of electrodes, each group of electrodes possessing an intra-group electrode spacing; a frame member comprising first and second arms, the frame member comprising an inner lumen for removably housing the at least one percutaneous lead, each arm of the first and second arms comprising a plurality of apertures that are spaced according to the intra-group electrode spacing to allow conduction of electrical pulses from the electrodes of the at least one percutaneous lead to tissue of the patient when the lead is positioned within the frame member; and a spring member that is connected to the frame member for maintaining the first and second arms of the frame member at a predetermined distance in the absence of an external force on the spring member.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/877,282, filed Oct. 23, 2007, now U.S. Pat. No. 8,019,442, whichclaims the benefit of U.S. Provisional Application No. 60/862,909, filedOct. 25, 2006, the disclosure of which is incorporated herein byreference.

BACKGROUND

The present application is generally related to an assembly kit forcreating paddle-style lead using one or several percutaneous leads andmethod of lead implantation.

Application of electrical fields to spinal nerve roots, spinal cord, andother nerve bundles for the purpose of chronic pain control has beenactively practiced for some time. While a precise understanding of theinteraction between the applied electrical energy and the nervous tissueis not fully appreciated, it is known that application of an electricalfield to spinal nervous tissue (i.e., spinal nerve roots and spinal cordbundles) can effectively mask certain types of pain transmitted fromregions of the body associated with the stimulated nerve tissue.Specifically, applying electrical energy to the spinal cord associatedwith regions of the body afflicted with chronic pain can induce“paresthesia” (a subjective sensation of numbness or tingling) in theafflicted bodily regions. Thereby, paresthesia can effectively mask thetransmission of non-acute pain sensations to the brain.

It is known that each exterior region, or each dermatome, of the humanbody is associated with a particular longitudinal spinal position. Thus,electrical stimulation of spinal nerve tissue must occur at a specificlongitudinal location to effectively treat chronic pain. Additionally,it is important to avoid applying electrical stimulation of nerve tissueassociated with regions of the body that are unaffected by chronic pain.Positioning of an applied electrical field relative to a physiologicalmidline is also important.

Percutaneous leads and laminotomy leads are the two most common types oflead designs that provide conductors that deliver stimulation pulsesfrom an implantable pulse generator (IPG) to distal electrodes adjacentto the nerve tissue. As shown in FIG. 1A, conventional percutaneous lead100 includes electrodes 101 that substantially conform to the body ofthe body portion of the lead. Due to the relatively small profile ofpercutaneous leads, percutaneous leads are typically positioned abovethe dura layer through the use of a Touhy-like needle. Specifically, theTouhy-like needle is passed through the skin, between desired vertebraeto open above the dura layer for the insertion of the percutaneous lead.

As shown in FIG. 1B, conventional laminotomy or paddle lead 150 has apaddle configuration and typically possesses a plurality of electrodes151 arranged in multiple columns. Multi-column laminotomy leads enablereliable positioning of a plurality of electrodes. Also, laminotomyleads offer a more stable platform that tends to migrate less afterimplantation and that is capable of being sutured in place. Laminotomyleads also create a unidirectional electrical field and, hence, can beused in a more electrically efficient manner than conventionalpercutaneous leads. Due to their dimensions and physicalcharacteristics, conventional laminotomy leads require a surgicalprocedure for implantation. The surgical procedure (a partiallaminectomy) is invasive and requires the resection and removal ofcertain vertebral bone tissue to allow both access to the dura andproper positioning of a laminotomy lead.

BRIEF SUMMARY

Some representative embodiments are directed to an assembly kit forreceiving one or several percutaneous leads. The assembly kit includes aframe member through which the percutaneous leads are threaded. Theframe member comprises first and second arms for receiving thepercutaneous leads. In each arm, the frame member comprises aperturesthat correspond to the positions and spacing of the electrodes of thepercutaneous leads. During assembly, the percutaneous leads are advancedthrough the frame member until the electrodes are exposed through theapertures. A spring member is attached to the frame member to provide amechanical bias to retain the arms with their leads at a desired widthwhen an external compressive force is not applied to the spring member.Also, a thin film member is preferably disposed between the first andsecond arms to prevent tissue in-growth between the two percutaneousleads after implantation.

During the implantation process, a suitable hollow-channel insertiontool is inserted within the epidural space of the patient according toone representative embodiment. The distal end with the spring member isinserted into the suitable hollow-channel insertion tool. The shape ofthe spring member allows the spring member and the arms of the framemember to be inwardly compressed to assume a relatively small profile.The compression of the spring member and the frame member enables theimplantation to occur through a relatively small insertion tool therebyreducing the trauma to the patient. The spring member, the frame member,and the lead(s) are advanced into the epidural space through theinsertion tool. Accordingly, removal of bone tissue is not required.Upon exiting the insertion tool, the spring member causes the arms ofthe frame member to be separated by the desired amount of space andthereby cause the electrodes of the stimulation lead(s) to be positionedin a manner similar to a paddle lead. The stimulation leads can then beutilized for spinal cord stimulation and the relative positions of theelectrodes will remain fixed. Also, the field applied by the electrodeswill be substantially unidirectional.

The foregoing has outlined rather broadly certain features and/ortechnical advantages in order that the detailed description that followsmay be better understood. Additional features and/or advantages will bedescribed hereinafter which form the subject of the claims. It should beappreciated by those skilled in the art that the conception and specificembodiment disclosed may be readily utilized as a basis for modifying ordesigning other structures for carrying out the same purposes. It shouldalso be realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the appendedclaims. The novel features, both as to organization and method ofoperation, together with further objects and advantages will be betterunderstood from the following description when considered in connectionwith the accompanying figures. It is to be expressly understood,however, that each of the figures is provided for the purpose ofillustration and description only and is not intended as a definition ofthe limits of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict conventional percutaneous and paddle leadsrespectively.

FIG. 2A depicts a paddle-style assembly kit for percutaneous leadsaccording to one representative embodiment. FIG. 2B depicts adisassembled view of a frame member and spring member according to onerepresentative embodiment.

FIG. 3 depicts a percutaneous lead adapted according to onerepresentative embodiment.

FIG. 4 depicts a “rear” view of a frame member and spring memberaccording to one representative embodiment.

FIG. 5 depicts a stimulation system according to one representativeembodiment.

DETAILED DESCRIPTION

Referring now to FIG. 2A, assembly kit 200 is shown according to onerepresentative embodiment. Assembly kit 200 comprises frame member 202that comprises parallel arms. Frame member 202 is preferably fabricatedfrom a relatively high durometer, biocompatible, biostable polymer.Examples of suitable polymers include polyetheretherketone (PEEK) andpolyether-ketone ketone (PEKK). Frame member 202 comprises a set ofapertures 204 on each arm of frame member 202 (which are showncollectively as 204 a-204 f). Apertures 204 can be formed by ablatingthrough the polymer material using a suitable laser. Although only sixapertures are shown in FIG. 2A for the sake of clarity, any number ofapertures can be provided in frame member 202 to accommodate suitablepercutaneous leads 201. Apertures 204 cause the field from electrodespositioned underneath apertures 204 to be substantially unidirectional.The unidirectional characteristic is advantageous, because it reducesthe probability of undesired stimulation in spinal cord stimulationapplications. Also, the unidirectional characteristic enablesstimulation to occur at a reduced power consumption.

Assembly kit 200 further comprises spring member 203 that is attached toframe member 202. Spring member 203 may be permanently attached to framemember 202 during fabrication of these components or may be fabricatedas a separate component for attachment by a surgeon. When assembled asshown in FIG. 2A, frame member 202 and spring member 203 can becollapsed to assume a relatively small profile to enable kit 200 to beinserted through a suitable implantation tool. An example of a surgicaltool that can be utilized to implant kit 200 is described in U.S. PatentApplication Publication No. 20050288759, entitled “Method and apparatusfor implanting an electrical stimulation lead using a flexibleintroducer,” which is incorporated herein by reference. When kit 200exits the introducer instrument into the epidural space, spring member203 is no longer subjected to a compressive force and expands the armsof frame member 202 to the predetermined distance. Hence, electrodes oflead(s) 201 are then positioned within the epidural space in a mannerthat is similar to an electrode spacing provided by a paddle-style lead.

One advantage of allowing the surgeon to attach spring member 203 duringthe implantation procedure is that multiple sets of spring members 203could be provided with each set having different spring characteristics.The surgeon could select a spring member 203 having a greater springconstant if assembly kit 200 does not sufficiently expand in theepidural space using another spring member 203 due to fibrosis or othertissue obstructions. Additionally, to prevent fibrosis or other tissuein-growth from occurring after implantation, thin membrane 205 isprovided between the arms of frame member 202. Thin membrane 205 can befabricated from a low durometer, elastic Carbosil material as anexample. By utilizing membrane 205, kit 200 can be more readilyexplanted if subsequently necessary.

Spring member 203 is also preferably fabricated from PEEK material whichpossesses a spring memory characteristic. Other suitable biocompatible,biostable polymers can be employed such as PEKK. If spring member 203 isfabricated as a separate component from frame member 202 as shown inFIG. 2B, complementary connector structures (not shown) are provided onframe member 202 and spring member 203 to facilitate their coupling. Insome alternative embodiments, metal spring elements are provided withinspring member 203 to provide or augment the spring characteristic ofspring member 203. However, metal spring elements can cause undesiredtissue heating during an MRI procedure due to current induction from thestrong time-varying RF fields generated by the MRI system. Accordingly,an all plastic structure is preferred to avoid current induction duringan MRI procedure.

Spring member 203 is also preferably shaped so that when the end ofspring member 203 encounters the inner wall of an insertion tool, thecontact force tends to “pinch” spring member 203 thereby providing acompressive force to spring member 203. In response to the compressiveforce, spring member 203 collapses the arms of frame member 202 therebyallowing kit 200 to assume a profile that allows kit 200 to be advancedthrough the insertion tool.

Any suitable percutaneous lead(s) 201 can be employed within kit 200provided that the electrode spacing of the lead(s) 201 corresponds tothe spacing of apertures in frame 202. In one embodiment, a respectivepercutaneous lead is inserted within each arm of frame member 202. Anexample of a suitable commercially available lead for assembly kit 200is the Axxess® lead available from Advanced Neuromodulation Systems,Inc. (Plano, Tex.). To retain each percutaneous lead 201 within frame,retention clips 207 are provided. Additionally, retention clips 207facilitate the removal of frame member 202 from the epidural space whenleads 201 are explanted.

In one embodiment as shown in FIG. 3, a single lead is adapted to bethreaded through both arms of frame member 202 of an assembly kit.Specifically, first and second groups 301 and 302 of electrodes aredisposed on the single lead. Electrode groups 301 and 302 are disposedsomewhat in the “middle” of the body of the lead. The intra-groupelectrode spacing in the lead corresponds to the spacing betweenadjacent apertures 204 in frame member 202. Also, the two groups ofelectrodes are separated on the body of the lead by distance 303 thatcorresponds to the distance between the two most distal apertures (204 cand 204 f in the specific embodiment of FIG. 2) including the distancealong spring member 203. The lead as shown in FIG. 3 also comprisesrespective groups of terminals 304 and 305 at the proximal and distalends of the lead. Each terminal of the groups 304 and 305 iselectrically coupled to a respective electrode of groups 301 and 302 bya respective conductive wire embedded within the insulative body of thelead. The positioning of the groups 301, 302, 304, and 305 of electrodesand terminals enables lead 201 to be looped through kit 200. The loopingof the lead through kit 200 is advantageous for explantation of framemember 202 and spring member 203.

Also, to facilitate explantation, the proximal portion of frame member202 is shaped at locations 206 a and 206 b to contact the inner wall ofthe insertion tool as shown in FIG. 4. In an explantation procedure,frame 202, spring member 203, and lead 201 are removed from the epiduralspace of a patient through the same type of surgical tool used for theimplantation procedure. Essentially, the surgeon places the tool overthe proximal ends of the lead and advances the tool until the epiduralspace of the patient is accessed. In a preferred embodiment, astrengthening wire member is inserted within an inner lumen of the leadto facilitate the explantation.

After insertion of the strengthening wire member and positioning of theopen channel tool, the surgeon “pulls” on the lead and the strengtheningwire member. The pulling force causes the lead, frame member 202, andspring member 203 to move up to the distal end of the tool. When theproximal end of frame member 202 contacts the inner wall of the tool,the resulting force pushes against locations 206 a and 206 b and theforce is transferred from the arms of frame member 202 to spring member203. The transferred force tends to elongate the frame and spring member203 thereby compressing spring member 203 and bringing the arms of frame202 together. Accordingly, the profile of frame 202 is reduced therebyallowing the kit 200 to be received within the open channel of the toolfor removal from the epidural space.

In such a procedure, the benefit of looping the lead within the kit 200is realized. Specifically, the looping of the lead enables thestrengthening wire member to follow the entire perimeter of frame member202 and spring member 203. Accordingly, a sufficient amount of force canbe readily applied to ensure that spring member 203 is compressed toallow the withdrawal of the kit 200 through the surgical tool.Additionally, it shall be appreciated that explantation proceduresaccording to representative embodiments involve relatively littlecomplexity and do not require overly delicate manipulations.

FIG. 5 depicts stimulation system 500 according to one representativeembodiment. System 500 comprises implantable pulse generator 501. Anexample of a commercially available pulse generator that can be usedaccording to some representative embodiments is the Eon® stimulatoravailable from Advanced Neuromodulation Systems, Inc. Pulse generator501 is electrically coupled to lead 201 which is threaded throughassembly kit 200. Lead 201 can be implanted in a patient withoutperforming a laminectomy using a suitable implantation tool. Afterimplantation in the epidural space of a patient, the positioning of theelectrodes as provided by kit 201 allows lead 201 to function in amanner similar to paddle-style leads.

Although representative embodiments and advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the appended claims. Moreover, the scope of the presentapplication is not intended to be limited to the particular embodimentsof the process, machine, manufacture, composition of matter, means,methods and steps described in the specification. As one of ordinaryskill in the art will readily appreciate from the disclosure thatprocesses, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized. Accordingly, the appended claims are intended to includewithin their scope such processes, machines, manufacture, compositionsof matter, means, methods, or steps.

What is claimed:
 1. An assembly kit for placing a stimulation lead forconducting electrical pulses from an implantable pulse generator totissue in a patient, the assembly kit comprising: a stiffening stylet;at least one percutaneous lead comprising terminals and at least twogroups of electrodes, each group of electrodes possessing an intra-groupelectrode spacing, wherein the at least one percutaneous lead comprisesan internal lumen for receiving the stiffening stylet; a frame membercomprising first and second arms, the frame member comprising an innerlumen for removably housing the at least one percutaneous lead, each armof the first and second arms comprising a plurality of apertures thatare spaced according to the intra-group electrode spacing to allowconduction of electrical pulses from the electrodes of the at least onepercutaneous lead to tissue of the patient when the lead is positionedwithin the frame member; a spring member that is connected to the framemember for maintaining the first and second arms of the frame member ata predetermined distance in the absence of an external force on thespring member; and a tubular introducer for engaging the frame memberduring an implant or explant procedure; wherein (i) the frame membercomprises a proximal end that is adapted to engage the tubularintroducer, (ii) the internal lumen of the percutaneous lead is adaptedto permit the stiffening stylet to extend along an entire length of theframe member to form a single loop extending through the tubularintroducer and the first and second arms of the frame member, and (iii)application of a pulling force on the stylet when disposed in the singleloop causes the proximal end of the frame member to contact the tubularintroducer to collapse the frame member into the tubular introducer. 2.The assembly kit of claim 1 wherein the spring member exhibits a springcharacteristic from polyetheretherketone (PEEK) material.
 3. Theassembly kit of claim 1 wherein the spring member comprises a metalelement that provides a shape memory characteristic.
 4. The assembly kitof claim 1 wherein the frame member is fabricated frompolyetheretherketone (PEEK) material.
 5. The assembly kit of claim 1further comprising a thin membrane structure disposed between the firstand second arms of the frame member.
 6. The assembly kit of claim 1wherein the spring member is attached to a distal end of the framemember.
 7. The assembly kit of claim 6 wherein the spring member isremovable from the frame member.
 8. The assembly kit of claim 6 whereinthe spring and frame members are fabricated from polyether-ketone ketone(PEKK).
 9. The assembly kit of claim 1 wherein the at least onepercutaneous lead is a single percutaneous lead, wherein the first andsecond groups of electrodes are spaced apart on a body of the singlepercutaneous lead by a distance equal to a distance between most distalapertures of the frame member including a distance along the springmember.
 10. The assembly kit of claim 1 wherein the frame member furthercomprises one or several retention clips for retaining the at least onepercutaneous lead.